EP0910820A1 - Low voltage bias circuit for generating supply-independent bias voltages and currents - Google Patents
Low voltage bias circuit for generating supply-independent bias voltages and currentsInfo
- Publication number
- EP0910820A1 EP0910820A1 EP97919572A EP97919572A EP0910820A1 EP 0910820 A1 EP0910820 A1 EP 0910820A1 EP 97919572 A EP97919572 A EP 97919572A EP 97919572 A EP97919572 A EP 97919572A EP 0910820 A1 EP0910820 A1 EP 0910820A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- transistor
- current
- coupled
- terminal
- voltage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F3/00—Non-retroactive systems for regulating electric variables by using an uncontrolled element, or an uncontrolled combination of elements, such element or such combination having self-regulating properties
- G05F3/02—Regulating voltage or current
- G05F3/08—Regulating voltage or current wherein the variable is dc
- G05F3/10—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics
- G05F3/16—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices
- G05F3/20—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices using diode- transistor combinations
- G05F3/26—Current mirrors
- G05F3/262—Current mirrors using field-effect transistors only
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F3/00—Non-retroactive systems for regulating electric variables by using an uncontrolled element, or an uncontrolled combination of elements, such element or such combination having self-regulating properties
- G05F3/02—Regulating voltage or current
- G05F3/08—Regulating voltage or current wherein the variable is dc
- G05F3/10—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics
- G05F3/16—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices
- G05F3/20—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices using diode- transistor combinations
- G05F3/205—Substrate bias-voltage generators
Definitions
- Low voltage bias circuit for generating supply-independent bias voltages and currents.
- the invention relates to bias circuits for generating bias voltages and currents.
- a bias circuit can be used, for example, in mixed-mode CMOS integrated circuits in which analog and digital circuits are integrated on the same semiconductor body.
- a key building block needed in such circuits is a bias circuit providing supply-independent bias voltages and currents.
- high-frequency supply interference generally caused by the digital part of the circuit, has to be rejected to enable good-quality performance of the analog part.
- Figure 1 shows a threshold-referenced bias circuit known from P.R. Gray and R.G. Meyer, Analysis and design of analog integrated circuits, Second Edition, Wiley, New York, 1984, Figure 4.24a. It is not suitable for low supply voltage however, since it includes two stacked gate-source voltage drops of the transistors P A and N A , and a drain-source saturation voltage of transistor N B . Also this known bias circuit is not well-regulated against supply variations. It is an object of the invention to provide a bias circuit capable of generating supply-independent bias voltages and currents down to a low supply voltage.
- a bias circuit comprising: a first supply terminal, a second supply terminal, and a bias voltage terminal; a first current mirror comprising first and second transistors of a first conductivity type, having a current input terminal, a current output terminal coupled to the bias voltage terminal, and a common terminal coupled to the second supply terminal; a second current mirror comprising third and fourth transistors of a second conductivity type opposite to the first conductivity type, having a current input terminal, a current output terminal coupled to the current output terminal of the first current mirror and to the bias voltage terminal, and a common terminal coupled to the first supply terminal; current providing means coupled between the first supply terminal and the current input terminal of the first current mirror for providing a current to the input terminal of the first current mirror; a fifth transistor of the first conductivity type having a gate, a source coupled to the second supply terminal, and a drain coupled to the current input terminal of the second current mirror; resistive means coupled in parallel to the gate and the source of the fifth transistor; and - a sixth transistor of the second
- the bias circuit according to the invention operates down to a supply voltage equal to the sum of the threshold voltage and the saturation voltage. It generates a supply- independent threshold-referenced bias voltage relative to the first supply terminal, similar as the known bias circuit depicted in Figure 1.
- This bias voltage is equal to the gate-source voltage of the sixth transistor needed for a current having a value equal to the threshold voltage of the fifth transistor divided by the resistance of the resistive means. Changes in the supply voltage cause corresponding changes in the gate-source voltage of the fifth transistor. Therefore the current through the resistive means and the sixth transistor will change proportionally causing a change in the gate-source voltage of the sixth transistor and the bias voltage.
- the bias circuit may further comprise a seventh transistor of the second conductivity type, having a gate coupled to the bias voltage terminal, a source coupled to the first supply terminal, and a drain coupled to the drain of the fifth transistor.
- the seventh transistor may be added to provide a slight amount of positive feedback in order to increase the current of the fifth transistor for very low supply voltage and to maintain a constant bias voltage.
- Figure 1 shows a circuit diagram of a conventional bias circuit
- Figure 2 shows a circuit diagram of a bias circuit according to the invention.
- Figure 1 shows a conventional bias circuit.
- a supply voltage V DD is connected between a positive supply terminal VP and a negative supply terminal VN which serves as signal ground.
- the source of a PMOS transistor P A is connected to the positive supply terminal VP, whereas the interconnected gate and drain of transistor P A are connected to a bias voltage terminal BVT.
- the bias voltage V B is therefore equal to the gate-source voltage of transistor P A .
- the current supplied by resistor R B is forced to flow in transistor N A . and, in order for this to occur, the transistor N B must supply enough current into resistor R A so that the gate-source voltage of transistor N A is adapted to the current supplied by resistor R B .
- the current through transistor P A is equal to the current flowing through resistor R A which is proportional to the gate-source voltage of transistor N A .
- the bias voltage circuit thus generates a threshold-referenced bias voltage V B relative to the supply voltage V DD -
- the current through transistor P A is determined by the loop comprising the NMOS transistors N A and N B , and the resistors R A and R B .
- Scaled copies of the current through transistor P A may be obtained by means of one or more PMOS transistors P B with a source, gate and drain connected to, respectively, the positive supply terminal VP, the bias voltage terminal BVT and an bias current terminal BCT.
- the lowest possible supply voltage V DD is equal to the sum of the gate-source voltages of the transistors N A and P A and the drain-source saturation voltage of transistor N B .
- An increasing supply voltage V DD causes an increasing current through transistor N A and an increasing voltage over resistor R A . This in turn causes an increasing current through transistor P A and an increasing bias voltage V B .
- the bias circuit of Figure 1 is therefore not well-regulated against supply voltage variations.
- Figure 2 shows a bias circuit according to the invention.
- the bias circuit comprises a first current mirror CMl having a current input terminal IT1 , a current output terminal OT1 coupled to the bias voltage terminal BVT, and a common terminal coupled to the second supply terminal VN; and a second current mirror CM2 having a current input terminal IT2, a current output terminal coupled to the current output terminal OT1 of the first current mirror CMl and to the bias voltage terminal BVT, and a common terminal CT2 coupled to the first supply terminal VP.
- the current input terminal IT1 of current mirror CMl is coupled to the drain of a PMOS transistor P j , the source of which is connected to the positive supply terminal VP and the gate of which is connected to the negative supply terminal VN.
- the transistor P j provides a current to the current mirror CMl .
- the transistor Pj may be replaced by a resistor.
- the current input terminal IT2 of current mirror CM2 is coupled to the drain of a NMOS transistor N 3 , the source of which is coupled to the negative supply terminal VN.
- a resistor RS is connected between the gate and the source of transistor N 3 .
- the bias circuit further comprises a PMOS transistor P 2 with a gate coupled to the bias voltage terminal BVT, a source coupled to the first supply terminal VP, and a drain coupled to the gate of transistor N 3 , an optional PMOS transistor P 3 with a gate coupled to the bias voltage terminal BVT, a source coupled to the first supply terminal VP, and a drain coupled to the drain of transistor N 3 , an optional PMOS transistor P 6 with a gate coupled to the bias voltage terminal BVT and a source and drain coupled to the positive supply terminal VP, and one or more optional PMOS transistors P 7 with a gate coupled to the bias voltage terminal BVT, a source coupled to the first supply terminal VP, and a drain coupled to the bias current terminal BCT.
- a PMOS transistor P 2 with a gate coupled to the bias voltage terminal BVT, a source coupled to the first supply terminal VP, and a drain coupled to the gate of transistor N 3
- an optional PMOS transistor P 3 with a gate coupled to the bias voltage terminal BVT, a source coupled to the
- the current mirror CMl is implemented with NMOS transistors N, and N 2 .
- the sources of transistors N j and N 2 are connected to the common terminal CTl .
- the gates of the transistors N ] and N 2 are interconnected and also connected to the drain of transistor N, .
- the drain of transistor N> is connected to the current input terminal IT1 and the drain of transistor N 2 is connected to the current output terminal OT1.
- Current mirror CM2 is implemented with PMOS transistors P 5 and P 4 which are connected to the current input terminal IT2, current output terminal OT2 and common terminal CT2 in a fashion similar to the transistors N j and N 2 .
- the bias circuit operates down to a supply voltage V DD equal to the sum of a threshold voltage Vt of transistor P 2 and a drain-source saturation voltage V DS m of transistor N 2 .
- V DD a supply voltage
- Vt threshold voltage
- V DS m drain-source saturation voltage
- Transistor P j is a weak transistor, i.e. a transistor with a small width over length ratio (W/L) and small transconductance factor, in saturation.
- the current of transistor P j is attenuated by the mirror-ratio of current mirror CMl and forced to flow in transistor P 4 by the negative feedback loop consisting of transistors P 2 , N 3 , P 5 and P 4 . Since transistors P 4 and P 5 form a current mirror, the current of transistor N 3 is proportional of that of transistor P j .
- Transistor N 3 is chosen strong, i.e.
- the current of transistor P 2 is approximately equal to Vt/R, R being the resistance of resistor RS.
- the bias voltage V B is therefore equal to the gate-source voltage of transistor P 2 needed for a current of Vt/R through transistor P 2 .
- the bias current I B supplied by optional transistor P 7 will be proportional to Vt/R.
- Transistor P 6 acts as a compensation capacitor to stabilize the aforementioned negative feedback loop of transistors P 2 , N 3 , P 5 and P 4 .
- Transistor P 6 can be replaced with a capacitor connected between the positive supply terminal VP and the bias voltage terminal BVT. In applications where large or many transistors such as transistor P 7 are biased, transistor P 6 can be omitted since sufficient capacitance will then be present.
- An advantage of compensating in this way, rather than via the Miller-effect of a capacitor between the bias voltage terminal BVT and the gate of transistor N 3 is that high-frequency interference on the positive supply terminal VP is rejected when generating V B .
- bias circuit By replacing PMOS transistors by NMOS transistors and vice versa a bias circuit is obtained which generates a bias voltage relative to ground.
- the bias circuit of Figure 2 was designed for fabrication in a 1.2 ⁇ n-well digital CMOS process with a threshold voltage Vt of about 0.9 V for both N and P devices. The design details are given in Table 1. W and L denote the width and length of the transistor.
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Nonlinear Science (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Automation & Control Theory (AREA)
- Amplifiers (AREA)
- Control Of Electrical Variables (AREA)
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP96201415 | 1996-05-22 | ||
PCT/IB1997/000507 WO1997044721A1 (en) | 1996-05-22 | 1997-05-07 | Low voltage bias circuit for generating supply-independent bias voltages and currents |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0910820A1 true EP0910820A1 (en) | 1999-04-28 |
EP0910820B1 EP0910820B1 (en) | 2001-10-17 |
Family
ID=8224014
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP97919572A Expired - Lifetime EP0910820B1 (en) | 1996-05-22 | 1997-05-07 | Low voltage bias circuit for generating supply-independent bias voltages and currents |
Country Status (4)
Country | Link |
---|---|
US (1) | US5825236A (en) |
EP (1) | EP0910820B1 (en) |
JP (1) | JPH11511280A (en) |
WO (1) | WO1997044721A1 (en) |
Families Citing this family (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6046944A (en) * | 1998-01-28 | 2000-04-04 | Sun Microsystems, Inc. | Bias generator circuit for low voltage applications |
US6043702A (en) * | 1998-01-29 | 2000-03-28 | Sun Microsystems, Inc. | Dynamic biasing for overshoot and undershoot protection circuits |
DE69830469D1 (en) * | 1998-03-16 | 2005-07-14 | St Microelectronics Srl | Polarization voltage control circuit for floating sink in a semiconductor integrated circuit |
US6326836B1 (en) * | 1999-09-29 | 2001-12-04 | Agilent Technologies, Inc. | Isolated reference bias generator with reduced error due to parasitics |
FR2825806B1 (en) * | 2001-06-08 | 2003-09-12 | St Microelectronics Sa | POLARIZATION CIRCUIT WITH VOLTAGE AND TEMPERATURE STABLE OPERATING POINT |
US7071770B2 (en) * | 2004-05-07 | 2006-07-04 | Micron Technology, Inc. | Low supply voltage bias circuit, semiconductor device, wafer and system including same, and method of generating a bias reference |
US7161430B1 (en) * | 2004-10-04 | 2007-01-09 | National Semiconductor Corporation | Low voltage folded metal oxide semiconductor field effect transistor (MOSFET) amplifier circuit |
US7132887B1 (en) * | 2004-10-04 | 2006-11-07 | National Semiconductor Corporation | Low voltage semi-folded metal oxide semiconductor field effect transistor (MOSFET) amplifier circuit |
US7459961B2 (en) * | 2006-10-31 | 2008-12-02 | Avago Technologies Wireless Ip (Singapore) Pte. Ltd. | Voltage supply insensitive bias circuits |
TWI654510B (en) | 2017-03-24 | 2019-03-21 | 立積電子股份有限公司 | Bias circuit |
CN111818690B (en) * | 2020-07-06 | 2023-06-06 | 天津中科新显科技有限公司 | High-precision current scaling circuit and scaling method applied to display driving |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4618816A (en) * | 1985-08-22 | 1986-10-21 | National Semiconductor Corporation | CMOS ΔVBE bias current generator |
NL9001017A (en) * | 1990-04-27 | 1991-11-18 | Philips Nv | BUFFER SWITCH. |
JP2978226B2 (en) * | 1990-09-26 | 1999-11-15 | 三菱電機株式会社 | Semiconductor integrated circuit |
US5124632A (en) * | 1991-07-01 | 1992-06-23 | Motorola, Inc. | Low-voltage precision current generator |
-
1997
- 1997-05-07 WO PCT/IB1997/000507 patent/WO1997044721A1/en active IP Right Grant
- 1997-05-07 JP JP9541906A patent/JPH11511280A/en active Pending
- 1997-05-07 EP EP97919572A patent/EP0910820B1/en not_active Expired - Lifetime
- 1997-05-19 US US08/859,798 patent/US5825236A/en not_active Expired - Fee Related
Non-Patent Citations (1)
Title |
---|
See references of WO9744721A1 * |
Also Published As
Publication number | Publication date |
---|---|
WO1997044721A1 (en) | 1997-11-27 |
JPH11511280A (en) | 1999-09-28 |
EP0910820B1 (en) | 2001-10-17 |
US5825236A (en) | 1998-10-20 |
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